1. Field of the Invention
This invention relates to a device for protecting gauge glasses.
2. Description of the Prior Art
It is customary to determine the level of water in a steam boiler by means of an external liquid level glass gauge assembly. Such an assembly typically comprises a thick walled transparent tube held in position by an upper and lower valve body arrangement. The upper valve body is connected to that portion of the boiler which is permanently in the vapor state and the lower valve body is connected to that portion of the boiler which should always contain water. Accordingly, the level of liquid in the transparent tube indicates the level of the vapor/liquid interface inside the boiler.
The criteria for the use and maintenance of such sight gauges are well known and are set forth in the suggested Rules of Care of Power Boilers (1971 Edition) (Section VII, Sub Section C2 201 through 210 and C5 608 through C5 609 published by The American Society of Engineers, New York, N.Y.). Because of the high pressures and temperatures involved in steam boilers it is desirable to have a tight seal between the gauge glass and the gauge glass holding bodies. This seal is usually provided by means of a rubber gasket which is compressed into place by a sealing nut. It has been found in practice that under operative conditions it is virtually impossible to maintain an absolutely leak-proof seal due to the degradation of the gasket material under operating conditions. Unfortunately, it is impractical to replace the gasket as soon as degradation begins. Therefore, it is the usual practice to put up with a certain amount of degradation in order to avoid the expense and inconvenience of shuting down the boiler at inopertune moments. If the gasket deteriorates while the boiler is operating at a high temperature and high pressure, then three serious disadvantages arise. First, the leaking vapor in aerosol form settles onto the sight gauge and obscures the line of vision, thereby preventing accurate readings. Second, the continual presence of such liquids will eventually erode the surface of the gauge glass. Thirdly, as the liquids evaporate they leave behind previously dissolved solid materials. It has been found that unless these deposits of solid materials are either prevented or are immediately removed, they will eventually cloud up the entire sight gauge. It is often difficult and unsafe to keep sight gauges clean since the gauges are generally located at a height of about 14 ft. above ground floor level and in very close proximity to boilers operating at temperatures in the range of 400.degree. F.
The nature of this problem has been known for a good many years. One method for coping with the problem is to provide better sealing gaskets at both ends of the sight gauge. Devices for improving the sealing between both ends of the gauge glasses are discussed in U.S. Pat. Nos. 1,038,642 and 2,629,262. Alternatively, mechanisms have been proposed and used to help keep the gauges clean. One such solution is found in U.S. Pat. No. 1,234,191 to Mahaley, issued July 24, 1917 which discloses an automatic gauge glass wiper. Another GAUGE CLEANING DEVICE is disclosed in U.S. Pat. No. 2,206,006 to Hendrey issued June 25, 1940.
Another approach to the same problem is to provide the gauge with a deflector right below its upper gasket so as to carry the steam and condensate away from the surface of the glass itself. An early type of deflector is disclosed in U.S. Pat. No. 1,387,676 issued on Aug. 16, 1921 to P. I. Wright. An improvement in gauge glass deflectors is also disclosed in U.S. Pat. No. 3,862,572 issued on Jan. 28, 1975 to Orlin R. Norris, the inventor of the device disclosed herein.
The devices described in U.S. Pat. Nos. 1,387,676 and 3,862,572 are believed to be satisfactory under general working conditions. However, there still continues to be a need for an effective, inexpensive gauge glass protector which does not possess the disadvantages inherent in the prior art.
While the problems of the prior art discussed above refer to the use of gauge glasses on steam boilers, it will be appreciated by those of ordinary skill in the art that the same sight gauge problems may be equally applicable to oil/ammonia systems such as used in conjunction with refrigeration compressers, holding tanks for cryogenic or freezing liquids, heated or unheated, fired or unfired pressure vessels used at, below or above atomspheric pressure.